Video encoding method and device and decoding method and device

Abstract

A video encoding method, a video encoding apparatus, a video decoding method, and a video decoding apparatus are provided. The video encoding method includes producing a fast transform matrix based on a transform matrix which is used for frequency transformation on a block which has a predetermined size; producing a transformed block by transforming the block having the predetermined size by using the fast transform matrix; and performing scaling with respect to the transformed block in order to correct a difference between the transform matrix used for the frequency transformation and the fast transform matrix.

The invention claimed is: 
     
       1. A video decoding method comprising:
 receiving, by a video decoder, a quantized transform block; 
 determining, by the video decoder, a scaling constant for scaling of transform coefficients included in the quantized transform block based on a quantization parameter; 
 scaling, by the video decoder, the transform coefficients by using the scaling constant; and 
 inverse-transforming, by the video decoder, the transform block that includes the scaled transform coefficients, 
 wherein, where i denotes a remainder after the quantization parameter is divided by 6, the scaling constant for i=0 is 40, the scaling constant for i=1 is 45, the scaling constant for i=2 is 51, the scaling constant for i=3 is 57, the scaling constant for i=4 is 64, and the scaling constant for i=5 is 72, and 
 an inverse-transform matrix used for the inverse-transforming includes elements that are integers.